Contact systems in which the individual contacts in a first working step come to a stop against the electrical leads, and in a second working step are latched into the contact chambers of the plug, are used at present in the automotive sector in electrical plug connectors. So-called clean-body contacts, among others, are used in this context. In these contact systems, elements of the contact chambers deflect into recesses or undercuts of the contacts and thereby provide primary latching of the contacts. In multi-part contact chamber systems, two primary latching types for clean-body contacts are known. In both cases the latching arms, with their latching hooklets, usually emerge as injection-molded parts from the lower part of the contact carrier as parts of the contact chamber walls. The first latching type is characterized in that the latching arm is attached to the contact chamber wall at the level of the contact shoulder, and the latching hooklet engages into a contact undercut in the vicinity of the contact opening. The latching arm grows out, so to speak, in the insertion direction, and when retained is loaded substantially axially in compression. The second latching type is characterized in that the latching arm is attached to the contact chamber wall at the level of the contact opening, and the latching hooklet engages over the contact shoulder or into a corresponding opening in the vicinity of the contact shoulder. The latching arm grows out, so to speak, opposite to the insertion direction, and when retained is loaded substantially axially in tension. In order to enhance functional reliability, customers are now requiring correct primary latching of the latching hooklets to be ensured by the fact that after assembly of the contact, the position of the latching arms is tested. For the first latching type, so-called spacer elements made of plastic, which are inserted from the plug face between the backs of the latching arms and the wall located therebehind, are already known. If a latching arm is not in the correct location, for example because it is not completely snapped into the contact, the spacer element is blocked and the placement state of the contact must be checked. When the spacer element is completely inserted, it prevents (usually unmonitored) reopening of the primary latch, thereby securing the position of the latching arm.
A general disadvantage of such spacer elements is that an additional part is required in the plug connectors in order to check the primary latching hooks, which means additional cost for the connection as a whole. For the second latching type, no comparable spacer systems that allow the position of the latching arms to be tested and secured are known at present.
In the contact chambers of plug connectors having a large number of pins, the contacts that have been latched in primary fashion are usually additionally checked, by way of a so-called secondary locking system, in terms of their correct position in the contact chamber, and are additionally secured at their correct insertion depth upon failure of the primary latching system. Plug connectors having many pins utilize, in many cases, so-called preassembled and transversely displaceable secondary locking plates that, in a clear position, initially permit unimpeded placement of the contacts into the contact chamber and then, at the end of the placement operation, are shifted at least one-half contact-chamber width transversely to the contact-chamber axes. With their locking contours protruding laterally into the contact chambers, the secondary locking plates on the one hand test for the correct insertion depth of the contacts, and on the other hand ensure additional locking.